1. Field of the Invention
The present invention is directed to a system for presenting audio/video programs, and more particularly, to a system which is capable of presenting audio and video images without interruption during the loading of data from a storage device.
2. Description of the Related Art
Interactive multi-media systems are systems in which the flow of an audio/video presentation is adjusted in response to signals provided interactively by a user. An audio/video presentation (or program) includes the presentation of audio and/or video images. In the consumer market, interactive multi-media systems typically run game programs, entertainment programs or education programs (collectively audio/video programs), which are purchased by the user and loaded into the system. Consumer interactive multi-media systems are or have been available from such companies as Nintendo K.K., Sega Enterprises, Atari Corp., Commodore-Amiga, and The 3DO Company, among others.
One example of the game programs used in consumer interactive multi-media systems includes maze (or adventure) games. The maze game usually takes the form of the user playing the part of an Adventurer (e.g. a medieval knight, dragon slayer, or other action hero) journeying through an environment filled with enemies and objects. The programmer creates the environment. The environment is defined as the setting (or location) of the game. For example, the environment could be a medieval castle with dungeons and secret passageways. Alternatively, the environment could be a maze, town, enchanted forest or any other indoor or outdoor location. The enemies include animals, monsters, humans armed with weapons, robots or anything else designed to cause harm to the Adventurer. Objects typically include stationary objects which may or may not serve as an obstacle to the Adventurer.
These games often provide a task which an Adventurer must perform. The user receives points depending on how well the Adventurer (controlled by the user) performs that task. One example of such a maze game is where the user plays the part of an Action Hero (Adventurer) who must save various persons being held captive in a castle. The castle has many secret passageways and dungeons. Inside the castle are fighters and animals who attempt to kill the Action Hero. The Action Hero must fight off the animals and fighters, take valuables from the castle (receive points), and save those people being held captive.
Although the Action Hero is said to "move" through the environment, "fight off" animals and enemies, "take" valuables, and "save" people, of course the user does not actually perform real-life actions of moving, fighting, taking and saving. Rather, the system, under software control, simulates such activities in response to the user's manipulation of a user-input device. As used herein, references to actions performed by a user or character in the environment, are intended as a shorthand to refer to system-simulation of such actions so that the user appears to have performed the action. For example, the user may indicate a desire to move to the right, by pressing a right-arrow button on the joypad. What the user really intends, and what is intended herein by such a statement, is that an image of the Action Hero, on the display, be moved to the right relative to other images on the display. The system may accomplish this by drawing a new frame into a frame buffer in memory, with the image of the Action Hero represented in slightly different memory locations than in the previous frame, relative to other images represented in the frame buffer. The system would then display the new frame buffer on the display.
In the past, some manufacturers of consumer interactive multi-media systems have had to make significant compromises in the realism of sounds and video images created by the system, as well as game play choices, in order to maintain a low price for the consumer market. For example, memory is expensive. In order to keep the costs low, interactive multi-media systems are generally designed with memory smaller than the size needed to store an entire audio/video program. Typically, audio/video programs are stored on cartridges, cassettes, floppy disks, networks, compact discs (CD), a server on a cable television network, or other storage medium (collectively called storage devices). A compact disc is defined to include ROM and writable discs.
Because the entire audio/video program cannot always fit into memory, only a portion of the program is read from the storage device into memory at a time. Thus, audio/video programs are often broken up into a series of levels. For example, each floor of a multi-floor castle could be a level, or each room in a maze could be a level. The levels are chosen such that all of the software necessary to implement that level can fit in the memory of the interactive multi-media system at one time. Thus, when the presentation of the audio/video program begins, all the software necessary to implement level 1 of the program is loaded into memory. The user then interacts with level 1 of the game. Interacts is defined to include watching, listening, inputting information, playing along, etc. Most games allow the user to progress from level 1 to level 2 under defined circumstances. For example, some games allow the user to progress from level 1 to level 2 only when the user has achieved a certain success level at level 1. Other games allow the user to progress from level 1 to level 2 when the user has crossed a boundary.
Dividing a program into a series of levels generally results in fairly extensive data loading periods when the user progresses from one level to another level, as new data is retrieved to replace data that is no longer needed. Thus, when the user progresses from level 1 to level 2, there is generally idle time. This idle time generally takes the form of the screen freezing or repeating a sequence of video images and no action for a period of time. Thus, when the user finishes a level, the user then must endure idle time before the user can play the next level. Thus, the user's enjoyment of the audio/video presentation is impeded by idle time throughout the presentation.